Thermionic tube



A. N. LUCIAN THERMIONIC TUBE May 29, 1934.

Filed Jan. 12, 1929 4 fw erw/70K /frscne /K [a ca/z f y ad fr/legs ma v- 774mm/ Matentecl May 29, 1934 i.; SATES FFE THERIVHONIC TUBE Arsne N. Lucian, Philadelphia, Pa., assigner to Heatless Light Corporation, a corporation of Delaware My invention relates to electrical apparatus, having particular relation to thermionic tubes.

One object of my invention is to provide a sirnple, eflicient and compact alternating-current tube, wherein the usual alternating-current hum is eliminated to an extent heretofore considered impossible.

Another object of my invention is to provide a tube having an equipotential cathode, heating means therefor, and a third electrode, and means whereby said third electrode may be shielded from said heating means.

Still another object of my invention is to provide a vacuum tube with means, whereby the electromagnetic interaction between the heating means and the plate or grid may be prevented,

and the cathode maintained as a magnetic shield throughout its length.

A further object of my invention is to provide 0 an equipotential cathode with means, whereby the plate or grid may be electrostatically shielded from the heating means.

A still further object of my invention is to provide apparatus of the character described, wherein the lead conductors and the heating filament for the equipotential cathode are shielded from the plate or grid substantially the entire length of said filament and conductors.

Other objects and applications of my invention, as well as details of construction and opera tion, whereby my invention may be practiced, will be apparent more fully hereinafter, when taken in connection with the accompanying drawing, wherein Fig. l is a vertical, sectional view of a vacuum tube and its associated base member;

Fig. 2 is a bottom plan view of the vacuum tube base shown in Fig. l;

Fig. 3 is an enlarged perspective view of one ci" the filament insulators shown in Fig. l;

Fig. i is enlarged detail vertical sectional View of an alternative embodiment of my invenm tion;

Fig. 5 is a diagrammatic View of the heating r means shown in Fig. l with its associated transformer;

Fig. 6 is a similar View, but showing the connection of the heating means of Fig. i to its transformer and to ground;

Fig. is a detail view of the insulating tube with one portion thereof moulded around the lead conductors; and

Fig. 8 is an enlarged detail View of a portion of the device of Fig. 1; and

Fig. 9 is a detail View ci a modification.

As a result of considerable development work, I have found that a large part of the hum in alternating-current vacuum tubes is due to the absence or the inadequacy of the electromagnetic and electrostatic shielding of the grid and plate from the'heating ineans. One embodiment of my invention, which is particularly designed for complete and effective electromagnetic and electrostatic screening, is shown in Fig. 1, wherein a tube l is secured at a lower end 2 in a base member 3. The lower end portion 2 is provided with a re--entrant stein e which terminates at its upper end is a press 5.

One of the features of my invention is the molding the press 5 a molded portion 6 (Fig. 7) of a glass stem 7, the stem 7 containing therein a pair of insulatingly-spaced lead wires or conductors 8 and 9. ln practice, the conductors 8 and 9 are rst placed in the stern 7 in spaced relation, whereupon a portion e' is heated so as to cause the material to mold around the wires 8 and 9, securing them in insulatingly-spaced relation. The final step consists in placing the molded portion 6 in the upper end of the reentrant stem 4 and then molding the latter and the portion 6 of the stem '7 together, so as to form the composite press of Fig. l.

As shown in Fig. l, an end portion 11 of the stem 7 projects upwardly beyond the press 5 into the tube 1, constituting a physical shield for the lead wires 8 and 9. Upper ends l2 and 13 of these wires are connected tothe lower ends of a iilanient le, an upper endv l5 of which is connected to a hooi; 16 supported in a small insulating block 17 oi the character shown in 3. It is noted that the block 1'? is provided with a plurality of longitudinal recesses 18, sc that a plurality` of relatively small surface portions 19 may engage an adjacent inner side 2l of a surrounding tubu lar member 22.

in insulating member 23 (Fig. 3) similar to the member 17 is positioned within a lower open end 24 of the tubular member 22 and it is provided with spaced apertures 25 and 26 through which the adjacent end portions of the iilament 14 are threaded. The insulating member 23 is similarly provided with longitudinal recesses, so that surface contact between the member 23 and the tubular member 22 may be reduced to a minimum. Such relatively small insulating supporting members 17 and 28, with their minimum surface contact with the tubular member 22, permits a very great reduction in the electrical leakage between the filament 14 and the member 22.

The tubular member 22 is preferably formed of magnetic material, and it is provided with an outer surface coating 28 so as to form an electron emitting cduipotential cathode 29. A. grid 3l and a plate 32 are so positioned as to surround the cathode 29 and are connected lead conductors 33 and 34 to external Contact pins 35 and 36 eictending outwardly from a lower side oi the tube base 3.

In accordance with my invention, the of electrostatic elds of force, as well as electromagnetic lines of force, through the upper end ci the tubular member 22 is prevented by closing the same with a cap 37 of magnetic material. The electro-magnetic lines of force extending from the cap 37 are new shunted through the rnernber 22 to the lower end portion of the member 22. Moreover, the cap 37 serves to block the passage of electrons between the lament ll and the grid 31 and the plate 32, due to the electrostatic lines of force. Accordingly, one of the sources of hum in a vacuum tube is eliminated.

My invention further contemplates the conii plete shielding of the lower open end of the tubular member 22. This desired result is obtained by mountingasleeve 38 of insulating material such as quartz, lavite, on the outer side of a lower edge portion 39 ci the member 22 and extending the sleeve 38 over an upper edge portion fil oi stein end portion 11, shown in Fig. 1. Thus, the lead wires 8 and 9, as well as the heating means 14, is mechanically shielded from the grid 31 and the plate 32, inasmuch as such electrons as tend to pass from the heating means lll are blocked by the stem end portion 11 and the insulating sleeve 38. Accordingly, electrostatic shiel g is pron vided for the lower open end portion oi" the tubular cathode 29.

The electromagnetic shielding of the lower end portion of the heating means 14, as well as the adjacent portions of the lead conductors 8 and 9, is accomplished by mounting a sleeve l2 of metal or other magnetic material on the outer side of the quartz or lavite sleeve 34, the upper and lower ends of the sleeve ti2 over-lapping the cathode 29 and the stem end portion 11, as shown in Fig. 1. The sleeve 42 is connected by a conductor i3 to the cathode 29 and the latter is grounded by means of a lead conductor 44 extending from o, mid-point 45 in the cap 37 through the press 5 to a pin 46 mounted on the und rside of the tube base 3. Added protection may be provided positioning a sleeve i7 within the stern end per tion 11, so as to enclose the portion of the lead wires 8 and 9 between the press 5 and the filament 14. The sleeve ll'l is grounded on the tubu lar cathode 29 by means of a conductor 48. Such construction affords a very complete electromagnetic well as electrostatic shielding for the lower open end of the cathode 29, preventing the establishment of a substantial. static or magnetic field between the 'filament 14.. the lead conduc tors 8 and 9 and the grid and the plate 32. It :is noted that the insulating sleeve 3S may be omitted and the space between the lower end of the cathode 29 the upper end of the stem il may be closed by the magnetic shielding member 42 alone, as shown clearly in Fig. 9.

A further source or hum in alternating current tubes is present in that portion of the lead conductors 8 and 9 for the heating means 14 which is positioned in the base This source is eliminated in my invention by providing the conductor 8 with a tubular section i9 which extends upwardly from a bottoni wall oi? the base to a point 50 just below the lower edge of the press 5. A lower` end portion 52 of the conductor section Li9 is positioned below the bottom wall of the base 3 and is enclosed by a conducting sleeve 53.

A terminal pin 54 is positioned in the center of the lower end portion oi the conducting 'tube i9 and it insulator therefrom by means of a sleeve 55. lhe terminal. pin 54 may be extended below the lower end oi the tubular por tion 52 in order to insure contact with a co-acting soclret (not shown). The pin 54 is secured to a section 56 of `the lead conductor 9. The section 55 passes up through the center of the tube and it isconnected at 57 to a second section 58 of the lead conductor 9 which extends into the press 5. The positioning of the conductor section 55 in the center ol' the tubular conductor sftion 47 permits the latter to constitute a inagnetic shield, and it also assures that both sec tions shall be straight throughout their length, thereby preventing the establishment of an unbalanced magnetic field adjacent to the lead conductors 3S, 34 and 54.

In order that access may be had to the lower ends ci the filament and thv upper ends 12 and i3 ci the lead conductors 8 and 9, these parts oi' such length as to permit the positioning the lead ends 12 and 13 substantially midway between the end portion 11 and the adjacent end of the cathode 29. Such open space permits the ready spot-rambling oi the concluetors 8 and 9 to the iilament 14, whereupon said open space may be easily closed by the telescoping sleeves 23 and 42.

Fig. 5 illustrates the connection of the filament i l to a transformer 59 of conventional z noted that a secondary winding 6l or i'iausiornier 59 is connected at a midpoint 52 to ground by means ci? a conductor 63.

rlhe embodiment of my invention shown in ers :troni that of 1 principally in the grounding oi' the upper inidportion l5 of the filament l/l by means of a conductor 64 which extends from the hook 16 through an end wall 65 oi a supporting inember 65 and 'the cap 37 of the tubular member The supporting member e6, in addition to the end wall 65, provided with a pair of elongated side wall portions 67 and 68 which closely nt i? er side 69 oi the meinber Thus, the necesity for the insulating members 17 and 23 of Fig. 1 eliminated., with corrsspcnding simplicity in the construction of the tube. The orting structure 65, 66 made of highly znagnetic material, thereby adding to the shielding eiect of the cathode 29.

The lower ends of the side wall portions 67 and G8 abut nst an upper edge portion 'Il oi an insulating sleeve l2 or lavite or lilre material. The sleeve Y?. i., provided with a recess 73 adaptto receive lower end portion '74 of the tubular nier-aber shown in Fig. Il. The insulatiug sleeve 7.2 extends downwardly over an upper end portion l5 oi' the stein end portion ll and is provided with an elongated recess '76 adapted to receive shoulder 77 formed on the 1 portion ll.

When the insulating member 72 is moved downwardly into the position shown in dot-anddash lines in l, access afforded to an open ce is betr an the upper end ofthe stem end portion l1 and the lower end of the tubular ineinber 22, permitting the spot-welding of adjaceirU end portions 79 and 8l oi conductors 8, 9 and the heating means lll. When it is de sired to return the insulating sleeve 72 to its normal position it is moved upwardly into the CII position of Fig. 4 and then turned slightly, so that the shoulder 7'? is not in line with the recess 75.

A conducting sleeve 82 of magnetic material is mounted on the outer side or the insulating sleeve 72 and is connected by means of a conductor 83 with the tubular conductor 22, whereby electrostatic and electromagnetic shielding may be afforded the iilarnent le and the lead conductors 8 and 9, as in Fig. 1. rlhe stern end portion l1 may also be provided a sleeve Se of magnetic material which is in contact with the inner surface thereof. The sleeve 8a is grounded by means of conductor sections 85 and 86 extending to the tubular cathode 29. Here again, the insulating sleeve 'l2 may be omitted noted in connection with Fig. 1.

Fig. 6 illustrates the connection of the heating means le of Fig. 4 to a transformer 84 and to ground. The structure of Fig. 4 is otherwise described in connection with Fig. l.

While I have shown only two embodiments of my invention, for the purpose of describing the same, it is apparent that various modifications may be made therein, without departing from the spirit of my invention.

I claim:

l. A tube having a press provided with a plurality of lead conductors projecting therefrom,

heating means connected. to said lead conductors, a cathode for at least partially enclosing heating means, auxiliary means for completely enclosing said lead conductors, and insulating means for positioning said auxiliary means relative to said cathode.

2. A tube provided with a press having a plurality of lead conductors projecting therefrom, heating means connected to some of said lead ,l conductors, a cathode for completely enclosing a portion of said heating means, means for at least partially enclosing said lead conductors, and means extending between said last-mentioned means and said cathode for completely enclosing the point of connection of said cathode and said lead conductors.

3. A tube having a plurality of electrodes including a cathode, a press, conductors extending therefrom, and a plurality of relatively movable ,y metallic telescopic members supported by said 4press and surrounding some of said conductors,

said telescopic members being in direct contact with each other and one of which constitutes the said cathode of the tube.

1l. A tube having an anode, cathode and control electrode, and means for heating said cathode provided with lead conductors extending through a press, one or" said conductors being positioned co-axially with respect to another throughout their entire length exterior to said press, whereby the fields of said pair of conductors may substantially neutralize.

5. In a tube having an anode, cathode and control electrode, means for heating said cathode provided with a plurality of conductors extending length exterior to said press, whereby a non-inductive condition may be maintained.

7. A tube having a press, a base, and conductors extending -irorn said press into said base, one of said conductors surrounding another throughout their entire length exterior to said press, whereby the magnetic held between two of said conductors may be substantially neutralized.

8. The combination in a therniionic vacuum tube having an anode, cathode and control electrode, of a press, conductors extending therefrom, and a plurality of relatively movable telescopic members formed or" magnetic material supported by said press and surrounding some of said conductors so as constitute a magnetic shield therefor, said telescopic members being in direct contact with each other and one of which constitutes the said cathode oi the tube.

9. The combination in a thermionic vacuum tube having an anode, cathode and control electrode, of a press, conductors extending therefrom, and a plurality or" telescopic members formed of magnetic `material supported by a tubular extension or said press and surrounding some of said conductors so as to constitute a magnetic shield therefor, said telescopic members being in direct Contact with each other and one of which constitutes the said cathode of the tube.

10. A thermionic vacuum tube having a press, conductors extending from said press, a tubular extension integral with said press and partially enclosing some of said conductors, and a plurality oi' telescopic members relatively movable with espect to each other and in direct contact with each other supported by said extension.

1i. A therniionic vacuum tube having a press, conductors extending from said press, a tubular extension integral with said press and partially enclosing some of said conductors, a plurality of telescopic members in direct contact with each other supported by said extension, and locking means on said extension for locking said telescopic members in desired position thereon.

12. A therrnionic vacuum tube having a press, conduct extending from said press, a tubular extension integral with said press and partially enclosing some of said conductors, and a plurality or telescopic members in direct contact with each other supported by said extension, said tubular extension having a magnetic shield positioned therein out or Contact with said lead conductors.

i3. In a thermionic vacuum tube having an anode, cathode and control electrode, ineans for heating said cathode, a press, a base and conductors leading from said anode, cathode, control electrode and said heating means 'and extending from said press into said base, one of the conductors of said heating means surrounding another whereby the magnetic field between the two conductors of said heating means may be substantially neutralized, and a terminal for said heating conductors comprising two coaxial conductor members separated by insulating material, one of said conducting members extending below the other or said members.

le. The combination in a thermionic vacuum tube having an anode, cathode control electrode, or" a press, conductors extending therefrom,

and a plurality of relatively movable members formed of magnetic material extending from said press and surrounding seine of said conductors so as te constitute a magnetic shield therefor, said members being in direct contact with each other.

15. In a thermionic vacuum tube having an (whereby the magnetic field between the two conductors of said heating means may be substantially neutralized), and. a terminal for said heating conductors comprising two Coaxial Conductor members separated by insulating material, one of said conductine' members extending below the other of said members.

ARSENE N. LUCIAN. 

